Beams, joists and frames for construction work, for example in aeronautics, civil engineering or architecture, are designed to withstand bending forces acting perpendicular to the direction of extension of the respective beams. Conventional beams may be implemented as an integral part with flanges at the edges and a web spanning between the flanges. Alternatively, instead of a web, cutter milled struts may be implemented between parallel running longitudinal support bars, thus leading to decreased weight of the beam due to less material being used to form the beam. Such struts may be employed in three-dimensional truss structures, as for example disclosed in documents EP 0 986 685 B1 or EP 1 358 392 B1.
Local load introduction into such beams or frames may, however, lead to torsional moments that are introduced into the attachment joints of the struts with the longitudinal support bars. Such torsional moments may in turn lead to additional moments within the longitudinal support bars that will have to be compensated for by local strengthening means, thereby nullifying some or all of the weight advantages gained.
Document U.S. Pat. No. 6,622,447 B1 discloses a modular structural system for building models and structures, using a plurality of connector hub members with spherical symmetry, and a plurality of strut members with longitudinal symmetry, wherein the strut members are removably engageable with the connector hub members placing the strut members in corresponding radial and tangential positions relative to the connector hub members.
Document CA 2 237 020 A1 and DE 38 00 547 A1 each disclose a set of structural elements for producing supporting structures, using supporting bars and cylindrical connecting elements for insertion heads provided on the end sides of the supporting bars.
Document DE 37 36 784 A1 discloses a node-truss system with rod-shaped elements which are pivotally connected to node bodies. Document U.S. Pat. No. 4,161,088 A discloses a pipe-and-ball truss array in which the outer chord of the truss array comprises an outer hollow pipe element having a structural tee element extending radially outward from the outer surface thereof in a plane normal to the plane in which the deck surface is to be supported on the truss array and an inner rod running through the pipe along the longitudinal axis thereof. A hollow substantially ball-like member, such as a hollow spherical member, is provided which is common to a plurality of truss members which truss members are joined to the spherical member by bolting.
Depending on the specific application, it may be advantageous to mount rods or struts via joints inside a framework in such a way that rotations of the rods or struts around their longitudinal axes within the respective joints are completely or at least partially prohibited. The joints may particularly function in way similar to universal joints with rotational/torque stiffness. In some applications, it may be further advantageous to provide frameworks with rod- or strut-like connections that are adjustable in length. Such adjustable connections may for example be employed for tolerance compensation of general framework structures or, for example, for moving certain parts of a vehicle with respect to other parts of the vehicle, e.g. aircraft flaps. Other applications, particularly in the aeronautics field, that rely on adjustable framework connections deal for example with adaptable structures, so-called morphing structures, e.g. adaptable aircraft wings with variable geometry and shape that consist of adjustable frameworks.